The Resting Membrane Potential Flashcards
How is the RMP expressed?
The voltage inside relative to the outside
What is a membrane potential?
An electrical potential difference across a cell’s plasma membrane
What is the RMP range for a nerve cell?
-50 - -90mV
What is the main ion involved in setting up the RMP?
K+
When potassium channels are open, in which direction does potassium move?
Out of the cell, down its concentration gradient
What are the intracellular and extracellular concentrations of potassium?
Intracellular: 160mM
Extracellular: 4.5mM
What does the Nernst equation calculate?
The equilibrium potential of an ion
How is the equilibrium potential of potassium (Ek) reached in a resting cell membrane? (Imagine there are no other ions involved)
Potassium channels are open so potassium diffuses out down its concentration gradient
This makes the cell negative and this opposes outflow of K+
Some potassium moves back in until an equilibrium is reached (Ek)
This potential difference is the the Ek
Is the resting membrane potential more or less negative than Ek?
Less negative
What effect does increasing the concentration of potassium extracellulary have on the RMP?
Makes it more positive
Define depolarisation
Decease in membrane potential so that inside the cell becomes less negative
Define hyperpolarisation
An increase in membrane potential so that inside the cell becomes more negative.
Which ions have a positive equilibrium potential and which have a negative one?
Positive: Na and Ca
Negative: K and Cl
Opening Na or Ca will hyperpolarise or depolarise the RMP?
Depolarise
What is mechanical gating?
When an ion channel opens/closes in response to membrane deformation
What can the membrane potential be measured by?
A microelectrode
What can the resting potential of an animal cell be in the range of?
-20 to -90mV
What can the resting potential of a cardiac/muscle cell be in the range of?
-80 to -90mV
How does increasing the permeability of an ion affect the RMP?
It moves it closer to the equilibrium potential of that ion
What is the equilibrium potential of an ion?
The membrane potential at which there is no net movement of the ion across the membrane
What is the difference between fast and slow synaptic transmission?
Fast synaptic transmission - the receptor protein is also an ion channel. The binding of the transmitter causes the channel to open.
Slow synaptic transmission - the receptor protein and ion channel are separate proteins. May be linked by G proteins or intracellular messengers
Name some transmitters at excitatory synapses
Acetylcholine
Glutamate
Name some neurotransmitters at inhibitory synopses
Glycine
γ-aminobutyric acid (GABA)
What do excitatory synapses cause?
Membrane depolarisation
An excitatory post synaptic potential (EPSP)
What do inhibitory synapses cause?
Hyperpolarisation
Inhibitory post synaptic potential
Which protein is the most important in allowing ionic movement to establish RMP?
Voltage-insensitive potassium channels
In hyperkalaemia, does the RMP become more positive or negative?
Positive
In hyperkalaemia, is it harder or easier for an action potential to be fired?
Easier because the RMP is closer to the threshold
Activation of the glycine receptor results in membrane hyperpolarisation or depolarisation?
Hyperpolarisation
Which ion is the glycine receptor permeable to?
Chloride
Inhibitory postsynaptic potentials may be elicited by opening channels for which ions?
Potassium and chloride
Excitatory postsynaptic potentials may be elicited by opening channels for which ions?
Sodium and calcium
